🐛 [BUG]水波图的外边框间距和背景颜色不能同时设置透明

### 🐛 Bug description [Please make everyone to understand it]
水波图的外边框间距和背景颜色不能同时设置透明
> Please provide a link by forking these links [G2Plot]or GitHub repo, a minimal reproduction.

* _Required_ **Link to minimal reproduction**:

### 📷 Step to reproduce
1.水波图案例设置外边框间距，设置theme主题色之后间距透明；
2.然后要是想让背景也透明的话，间距消失了；
3.猜测应该是背景色和间距的透明度是正好相反的，其中一个为1，另一个就为0，从下图所猜测；

### 🏞 Expected result
同时能设置两个都透明

### 🚑 Any additional [like screenshots]

* **G2Plot Version**:2.4.10
* **Platform**:

Start by reproducing the water-wave chart behavior in G2Plot 2.4.10 using the issue's two transparency settings: outer spacing and background color. Inspect the water-wave chart's theme and spacing configuration to determine why setting both transparent makes the spacing disappear. Done means both settings can be transparent at the same time without the outer spacing disappearing.

Written by the indexing model from the issue text.